The long-term goal of this research program is to develop an optical magnetometer for use in fetal magnetocardiography (fMCG) and fetal magnetoencephalography {fMEG) systems. We believe that the proposed magnetometer, based on a major recent discovery,represents the first viable alternative to SQUID magnetometers; thus,the potential impact of the research on the field of biomagnetism is enormous. Utilization of fMCG and fMEG has been limited by the high cost of acquisition and maintenance associated with SQUID technology. The optical magnetometer can mitigate these disadvantages while n maintaining or even surpassing the magnetic field sensitivity of SQUID magnetometers. Thus far only the high sensitivity of the device has been demonstrated. The short-term goal of the research is to construct a device that is practical for human studies, while maintaining the high magnetic field sensitivity. The specific aims are: 1. To build a optical magnetometer/gradiometer that utilizes rubidium atoms and achieves a magnetic field sensitivity 10A-14 T/(Hz)A1/2. 2. To construct a miniaturized prototype magnetometer that would be practical for fetal n magnetocardiography. 3. To evaluate the performance of the magnetometer by assessing its signal and noise characteristics and by conducting phantom studies. 4. To justify classification of the magnetometer as a nonsignificant risk by assessing and eliminating n potential safety hazards.